Kathryn Bigelow is looking for a large group of Twitter users willing to send a single message simultaneously this Friday in support of women in national security. And it’s no coincidence that her effort also serves to advertise her latest film, Zero Dark Thirty.

The director -- and Sony -- have enlisted Thunderclap, which will help gather at least 500 people who support their cause to tweet en masse: “Join me in saluting the crucial role women play in America’s national security #ZeroDarkThirty http://thndr.it/RUiqAe.”

Thunderclap is a nine-month-old startup from De-De, a development company backed by advertising firm Droga5. At its site, civic-minded folks explain their cause and ask supporters to allow Thunderclap to automatically re-tweet the pre-determined message at the appointed time. The message can also go on the Facebook walls of the supporters.

To make money, the company sells branded campaigns for up to $20,000, and Zero Dark Thirty is its biggest movie client so far. The documentary film Escape Fire: The Fight to Rescue American Healthcare also used Thunderclap, and the independent film Girl Rising also is planning to use it, according the Thunderclap CEO David Cascino.

Before Sony and Zero Dark Thirty, the biggest entertainment campaign orchestrated by Thunderclap was for Discovery Channel, though Cascino said Thunderclap handled that one for free. The message that went out at 3 p.m. Aug. 15 was: “We support #SharkWeek conservation partners and want to keep our finned friends safe from extinction. http://thndr.it/NWTwOR.”

The social reach of the Shark Week promo was 1.8 million, according to Thunderclap. One of the company’s biggest successes, though, was when Beyonce promoted a Thunderclap for World Humanitarian Day with a video shot by Ridley Scott, according to Cascino. Thunderclap says the social reach of that effort exceeded 1 billion worldwide.

As for Zero Dark Thirty, Bigelow’s plea for support is featured on the homepage under the heading, “A Salute to Heroic Women.” Clicking the message not only brings users to the page where they can read the tweet and decide whether they’ll “support” it, but also to a trailer for Zero Dark Thirty and other promotional items.

Bigelow needs at least 500 people to support her, or the planned tweet will not go out. Cascino figures she won’t have a problem reaching the goal, since about 220 people -- with a social reach of 300,000 so far -- have already signed on, and sources say Sony will get behind plans to market the effort beginning Tuesday. Sony, though, didn’t respond to requests for comment.

“Thunderclap only works with interesting content. If you just say, ‘Go out and buy Cheetos,’ it won’t work well,” Cascino said. “But if there’s an interesting human element that people can identify with, it does well. For Zero Dark Thirty, the angle they’re after is women’s role in national security, which is typically a boys’ club. It goes with the girl-power, kicking-ass vibe, and if people identify with that, it could go very large."-The Hollywood Reporter